1. Field of the Invention
The present invention relates to an encapsulating sheet, an optical semiconductor device, and a producing method thereof, to be specific, to an encapsulating sheet, an optical semiconductor device including the encapsulating sheet, and a producing method thereof.
2. Description of Related Art
An optical semiconductor device is produced by encapsulating an optical semiconductor element such as an LED (a light emitting diode element) that is mounted on a board by an encapsulating layer and a phosphor layer that contain a silicone resin. By the encapsulating layer and the phosphor layer that contain the silicone resin, the durability of the optical semiconductor element is improved and in this way, the long-term reliability of the optical semiconductor device is improved.
To be specific, as a method for obtaining an optical semiconductor device, the following method has been proposed (ref: for example, Japanese Unexamined Patent Publication No. 2012-49508). That is, first, a blue LED is mounted on a board by wire-bonding; next, the blue LED and a wire that connects the blue LED to the board is covered with (is embedded by) an encapsulating material that is prepared from a silicone resin; and subsequently, the encapsulating material is cured, so that an encapsulating layer is formed. Separately, a silicone resin composition containing a platinum-carbonyl complex (a hydrosilylation catalyst) is prepared to be applied to the surface of a release substrate and a precursor layer is formed. The obtained precursor layer is heated, so that a phosphor layer that is prepared from a silicone resin composition in a B-stage state is formed. Thereafter, the phosphor layer is transferred onto the encapsulating layer that covers the blue LED and next, the phosphor layer is heated, so that the silicone resin composition of the phosphor layer is completely cured.